Markova, N.; Puls, J.; Scuderi, S.; Simon-Diaz, S.; Herrero, A. Spectroscopic and physical parameters of Galactic O-type stars. I. Effects of rotation and spectral resolving power in the spectral classification of dwarfs and giants. Astronomy & Astrophysics. 2011, 530: A11. Bibcode:2011A&A...530A..11M. arXiv:1103.3357v1. doi:10.1051/0004-6361/201015956.
Aller, A.; Miranda, L. F.; Ulla, A.; Vázquez, R.; Guillén, P. F.; Olguín, L.; Rodríguez-López, C.; Thejll, P.; Oreiro, R.; Manteiga, M.; Pérez, E. Detection of a multi-shell planetary nebula around the hot subdwarf O-type star 2MASS J19310888+4324577. Astronomy & Astrophysics. 2013, 552: A25. Bibcode:2013A&A...552A..25A. arXiv:1301.7210v1. doi:10.1051/0004-6361/201219560.
Getman, K. V.; et al. The Elephant Trunk Nebula and the Trumpler 37 cluster: contribution of triggered star formation to the total population of an H II region. Monthly Notices of the Royal Astronomical Society. 2012, 426 (4): 2917–2943. Bibcode:2012MNRAS.426.2917G. arXiv:1208.1471. doi:10.1111/j.1365-2966.2012.21879.x.
doi.org
Walborn, N. R.; Fitzpatrick, E. L. Contemporary optical spectral classification of the OB stars – A digital atlas. Publications of the Astronomical Society of the Pacific. 1990, 102: 379. Bibcode:1990PASP..102..379W. doi:10.1086/132646.
Markova, N.; Puls, J.; Scuderi, S.; Simon-Diaz, S.; Herrero, A. Spectroscopic and physical parameters of Galactic O-type stars. I. Effects of rotation and spectral resolving power in the spectral classification of dwarfs and giants. Astronomy & Astrophysics. 2011, 530: A11. Bibcode:2011A&A...530A..11M. arXiv:1103.3357v1. doi:10.1051/0004-6361/201015956.
Aller, A.; Miranda, L. F.; Ulla, A.; Vázquez, R.; Guillén, P. F.; Olguín, L.; Rodríguez-López, C.; Thejll, P.; Oreiro, R.; Manteiga, M.; Pérez, E. Detection of a multi-shell planetary nebula around the hot subdwarf O-type star 2MASS J19310888+4324577. Astronomy & Astrophysics. 2013, 552: A25. Bibcode:2013A&A...552A..25A. arXiv:1301.7210v1. doi:10.1051/0004-6361/201219560.
Getman, K. V.; et al. The Elephant Trunk Nebula and the Trumpler 37 cluster: contribution of triggered star formation to the total population of an H II region. Monthly Notices of the Royal Astronomical Society. 2012, 426 (4): 2917–2943. Bibcode:2012MNRAS.426.2917G. arXiv:1208.1471. doi:10.1111/j.1365-2966.2012.21879.x.
harvard.edu
ui.adsabs.harvard.edu
Walborn, N. R.; Fitzpatrick, E. L. Contemporary optical spectral classification of the OB stars – A digital atlas. Publications of the Astronomical Society of the Pacific. 1990, 102: 379. Bibcode:1990PASP..102..379W. doi:10.1086/132646.
The Draper Catalogue of stellar spectra photographed with the 8-inch Bache telescope as a part of the Henry Draper memorial, Edward C. Pickering, Annals of Harvard College Observatory27 (1890), Bibcode:1890AnHar..27....1P
Markova, N.; Puls, J.; Scuderi, S.; Simon-Diaz, S.; Herrero, A. Spectroscopic and physical parameters of Galactic O-type stars. I. Effects of rotation and spectral resolving power in the spectral classification of dwarfs and giants. Astronomy & Astrophysics. 2011, 530: A11. Bibcode:2011A&A...530A..11M. arXiv:1103.3357v1. doi:10.1051/0004-6361/201015956.
Aller, A.; Miranda, L. F.; Ulla, A.; Vázquez, R.; Guillén, P. F.; Olguín, L.; Rodríguez-López, C.; Thejll, P.; Oreiro, R.; Manteiga, M.; Pérez, E. Detection of a multi-shell planetary nebula around the hot subdwarf O-type star 2MASS J19310888+4324577. Astronomy & Astrophysics. 2013, 552: A25. Bibcode:2013A&A...552A..25A. arXiv:1301.7210v1. doi:10.1051/0004-6361/201219560.
Getman, K. V.; et al. The Elephant Trunk Nebula and the Trumpler 37 cluster: contribution of triggered star formation to the total population of an H II region. Monthly Notices of the Royal Astronomical Society. 2012, 426 (4): 2917–2943. Bibcode:2012MNRAS.426.2917G. arXiv:1208.1471. doi:10.1111/j.1365-2966.2012.21879.x.